The first step of this project is to produce the recombinant protein, research for a condition to refold the protein, and develop a process to purify to refolded recombinant protein.[unreadable] A gene encoding the Plasmodium falciparum Circumsporozoite (CS) protein has been designed, synthesized, and cloned into an E. coli expression vector. A clone expressing the recombinant CS protein (rCSP) was selected. The rCSP expressed as the inclusion bodies has an intact N-terminus, and is being characterized for disulfide linkages. The current effort is focused on finding a suitable buffer condition to refold the solubilized rCSP.[unreadable] We have generated several monoclonal antibodies (mAbs) using the C-terminal domain of a yeast produced CS protein as immunizing antigen. Six mAbs recognized the sporozoites and the native CS protein. Three of them are conformation-dependent mAbs, recognizing at least 2 independent epitopes. The other 3 mAbs recognized the CS repeats, are thus conformation independent. We are in preparation to test their ability to inhibit sporozoite invasion of hepatocytes.